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What is MRI ?
Magnetic Resonance Imaging is a
modern computerized method of scanning, creating images using a
strong magnetic field and radio waves. The hydrogen atoms in the
patient's body react to the magnetic field and emit signals which
are analyzed by a computer to produce images. The images obtained
help in detecting various abnormalities in the tissues scanned.
MRI is a non-invasive,
sophisticated diagnostic imaging technique that utilizes a strong
magnetic field in conjunction with low energy electromagnetic
waves to produce high-resolution images of internal body organs
and tissue from any angle and direction and without surgical
invasion. MRI has proven to be invaluable to the diagnosis of a
broad range of conditions, including
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brain tumors;
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disorders of the eyes and inner
ear;
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cancer;
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stroke and heart disease; and
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Joint and musculoskeletal
disorders and diseases of the knee, shoulder, spine, hips,
wrists and hands, where it allows evaluation of parts of the
body not possible with other imaging techniques.
MRI can also create images of
vessels without depending on the significant volume of contrast
agent required by X-ray angiography, which can cause tissue damage
in high doses and to which patients may be sensitive.
MR Angiography (MRA) allows the physician to:
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examine the structure and
functioning of the heart, aorta and blood vessels, and to
determine the extent of damage caused by a heart attack of
progressive heart disease;
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evaluate aneurysms,
arteriovenous malformations (AVMs) and occlusions of the intra
cranial vessels; and
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screen for atherosclerotic
plaques and abnormalities in the carotid and iliofemoral
circulation, including in the extremities, abdomen and chest.
MRA is also well suited for
evaluation of the slow flow present within the dural venous
sinuses and to rule out superior sagittal sinus thrombosis, and
also clearly depicts arteries in the Circle of Willis as well as
the proximal portions of the anterior, middle and posterior
cerebral arteries.
There are two types of MRI units;
high-field MRI and low-field, open MRI. In the former, the patient
lies still within a closed, cylindrical magnet while radio waves
are directed at protons, the nuclei of hydrogen atoms, which are
alternately excited and relaxed, emitting radio signals which are
then processed by a computer to form an image. In open MRI, the
patient is not fully enclosed.
High-field MRI produces superior
images in a shorter scan time and is preferred by most physicians.
Low field, open MRI is dictated for patients who are
claustrophobic or extremely large. Image quality is good but the
scan time is generally longer than the high-field unit. In
addition, several of our centers offer a high-field short bore
unit with a wide bore opening that is less claustrophobic and can
accommodate patients up to 500 lbs.
Importance
of MRI
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MRI is painless
and has no known side effects.
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It usually reveals
more details than other imaging modalities. Usually there is a
clear distinction between healthy and diseased tissue on MRI.
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Harmful effects of
radiation are avoided.
MRI does not
use X-rays or radiation.
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